The study, on which Army scientists at the Edgewood Chemical Biological Center near Baltimore also collaborated, has been called groundbreaking (though also controversial because one of the study's lead authors previously received funding from a maker of pesticides that some blame for CCD). The honeybee die-off strikes about 20 to 40 percent of commercial beekeepers in a good year, Henderson says, and up to 60 percent in a bad one. When it hits a beekeeping operation, it can take out up to 70 percent of its colonies.

How many bees have died since 2006? Some estimates suggest the total is in the billions. And it's not just U.S. honeybees that are affected: CCD has shown up in parts of Europe and elsewhere. According to a study released this month, U.S. bumblebees - which also are important pollinators - are facing a sharp decline, too. Recently we met with Henderson at the University of Montana in Missoula to talk about his research, career and getting stung.

- Rachel Saslow

What are some of the hypotheses floating out there to explain CCD?

There are three approaches. Some people have seriously considered climate change, others have focused on an accumulation of pesticides. The third approach was, maybe we've got a new disease we haven't identified before. We fell into that category.

Does the virus or the parasite hit the bees first?

We don't know which is first yet. What we think is unique is the parasite and the virus hitting the bees at the same time. That's causing the collapse.

You emphasize that this study did not prove that these two infections are to blame.

The first research was just finding a pattern. We collected bees in different colony collapse events and sent them off for analysis, and these two popped up 100 percent of the time. But that's not proof, that's just association.

What' s your next step?

Our next step is to isolate them and purify [the virus and the parasite] so we can infect a colony on our own, experimentally, and watch that colony die. That's what proves it.

Why does it matter if honeybees die?

When this hits a honeybee operation, it can take out 60 to 70 percent of bee colonies in the operation. It just drives the commercial beekeepers under. Besides financial losses, it reduces the number of bee colonies available for pollination services nationwide. Since we rely on bees to pollinate about one-third of our food base, the loss would reduce availability of those foods and increase prices.

How did you get interested in honeybees?

I had this broad background in animal behavior, but it was all small mammals: squirrels and mice and hares. Jerry Bromen-shenk, here at the university, had been doing a lot of honeybee research, and we started working together in '99 or 2000. I've developed a new appreciation for honeybees. They're really a complex and interesting animal. You see a lot of problem-solving and really fun behavioral ecology in honeybees that I probably didn' t ever appreciate when I was a student. It's neat stuff.

Are you a beekeeper?

We all are, research-wise, but I'm not a hobby beekeeper.

How many times have you been stung?

In a good year, like this year, I've only been stung half a dozen times. But there are seasons where we're moving bee colonies around at night and doing experiments where I'm stung 40 or 50 times in a season. You get the initial burn when the venom goes in, but after 10 minutes, I don't notice anymore.